fix typo in docs

Signed-off-by: Aleksandar Stojanov <me@fnd.works>

Author: losisin

docs/README.md

@@ -39,7 +39,7 @@ The following annotations are supported:
  * [required](#required)
  * [patternProperties](#patternproperties)
  * [additionalProperties](#additionalproperties)
- * [$id](#$id)
+ * [$id](#id)
 * [Meta-Data Annotations](#meta-data-annotations)
  * [title and description](#title-and-description)
  * [default](#default)